Uniqueness and Identity Rules in ORM

Transcription

1 Reference: Mustafa Jarrar: Lecture Notes on Uniqueness and Identity Rules in ORM Birzeit University, Palestine, 2015 Uniqueness and Identity Rules in ORM (Chapter 4) Mustafa Jarrar Birzeit University, Palestine 1

2 Slides And Videos - Download, Watch, Interact Watch this lecture and download the slides from Some diagrams in this lecture are based on [1] Keywords: Identity, Uniqueness, Cardinality, Business Rules, ﻩهﻭوﻱيﺓة, ﻑفﺭرﻱيﺩد, 2

3 Reference: Mustafa Jarrar: Lecture Notes on Uniqueness and Identity Rules in ORM University of Birzeit, Palestine, 2015 Uniqueness and Identity Rules in ORM Part 1: What is Uniqueness/Identity? Part 2: Internal Uniqueness (within a Fact Type) Part 3: External Uniqueness (across Fact Types) Part 4: Key Length and Reference Schema 3

4 Conceptual Schema Design Steps 1. From examples to elementary facts 2. Draw fact types and apply population check 3. Combine entity types 4. Add uniqueness constraints 5. Add mandatory constraints 6. Add set, subtype, & frequency constraints 7. Final checks, & schema engineering issues 4

5 Identity Criteria and Uniqueness In Data Modeling: One of more attributes (Name, Name+Birthday, ) that we can use to uniquely refer to an entity, within a contest! If we cannot easily find/use these attributes, we give an ID (ID number, Book number, URI, IRI.) In reality A property that can be used to uniquely refer to an entity in any context, if this property is changed then the entity becomes another (what identifies a person? Book?). Notice that an attribute/property should be mandatory/essential to be used for identification. (we will talk about this later). 5

6 What is Uniqueness? For each state taken individually, each person has at most one weight. è How can we record such information without redundancy? 6

7 Reference: Mustafa Jarrar: Lecture Notes on Uniqueness and Identity Rules in ORM University of Birzeit, Palestine, 2015 Uniqueness and Identity Rules in ORM Part 1: What is Uniqueness/Identity? Part 2: Internal Uniqueness (within a Fact Type) Part 3: External Uniqueness (across Fact Types) Part 4: Key Length and Reference Schema 7

8 Uniqueness on Unary Fact Types Is their any problem with this schema? How can we prevent people adding such redundant information? 8

9 Uniqueness on Unary Fact Types The uniqueness constraint ensures entities are unique (no duplicates) 9

10 Uniqueness on Binary Fact Types Each Politician was born in at most one Country Each Politician heads government of at most one Country Each Country has at most one head Politician 10

11 Uniqueness on Binary Fact Types Means many to many It is possible that the same Politician visited more than one Country and that the same Country was visited by more than one Politician Who can give more examples? 11

12 Uniqueness on Binary Fact Types What is unique here? 12

13 Uniqueness on Binary Fact Types What is unique here? 13

14 Uniqueness on Binary Fact Types The four uniqueness constraint patterns for a binary. No duplicates are allowed in a's column Each a R's at most one b No duplicates are allowed in b's column Each b is R'd by at most one a Both the foregoing constraints apply No duplicate (a,b) rows are allowed Each a may R many b and vice versa 14

15 How to think about Uniqueness Is the population significant? Adding counterexamples to test the constraints ü 15

16 Uniqueness on Binary Fact Types Which is more realistic? 16

17 Uniqueness on Ternary Fact Types What are the uniqueness constraints? Each (Person, Subject) combination is unique. 17

18 Uniqueness on Ternary Fact Types Allowed basic uniqueness constraints for a ternary. 18

19 Uniqueness on Ternary Fact Types What this uniqueness means? 19

20 Uniqueness on Ternary Fact Types Allowed uniqueness constraint combinations for a ternary. 20

21 Uniqueness on Ternary Fact Types Which of this constraint patterns is illegal? Why? û û û 21

22 Example of Uniqueness on n-ary fact types Each (a,c,d) combination occurs on at most one row. 22

23 Uniqueness with Nested Fact Types This constraint is particularly important! Why? è Explain what is unique 23

24 Reference: Mustafa Jarrar: Lecture Notes on Uniqueness and Identity Rules in ORM University of Birzeit, Palestine, 2015 Uniqueness and Identity Rules in ORM Part 1: What is Uniqueness/Identity? Part 2: Internal Uniqueness (within a Fact Type) Part 3: External Uniqueness (across Fact Types) Part 4: Key Length and Reference Schema 24

25 What is the difference between these? è Explain the Joins è Do we need uniqueness? 25

26 External Uniqueness constraints What is missing? u 26

27 External Uniqueness constraints The meaning of the External Uniqueness Each (b,c) combination is paired with at most one a Each population R join S has bc unique (where join denotes conceptual inner join ) 27

28 Example 28

29 An Other Uniqueness How to say that the combination of (Discipline, YearLevel, SerialNr) is unique for each subject? The Subject code might be generated from this combination 29

30 Example with nest fact types 30

31 Reference: Mustafa Jarrar: Lecture Notes on Uniqueness and Identity Rules in ORM University of Birzeit, Palestine, 2015 Uniqueness and Identity Rules in ORM Part 1: What is Uniqueness/Identity? Part 2: Internal Uniqueness (within a Fact Type) Part 3: External Uniqueness (across Fact Types) Part 4: Key Length and Reference Schema 31

32 Key Length Check What is wrong? Splits into Each UC in an elementary n-ary relationship must span at least n-1 roles 32

33 Key Length Check What is wrong? Splits into 33

34 Reference Schemes In data modeling, each entity (i.e., Object Type) must have an identity. The identity is achieved if an entity has mandatory and unique role è This is not important (i.e. implicit) in ontology modeling. 34

35 Project (Student Registry) Description: The central management of students profiles by the ministry of education is becoming an urgent need in the last years. Many students in Palestine move from one university to another, and they need to transfer their academic records. Also, the ministry of higher education needs to certify the diplomas and mark sheets of students. Moreover, there is a need to centrally manage/monitor students financial aids. Therefore, the ministry of higher education has decided to build a national student registry, such that, each semester every university has to send the academic record (i.e., mark-sheet) of every student to the ministry of education. The ministry will then update and integrate the academic records according to the data combined from all universities into the national student registry. The ministry wants to specify a data model (in ORM) to be used as a reference data model of, including the business rules. è Develop a conceptual model (in both Arabic and English separately) for this information system, which must be suitable for mark sheets in all Palestinian universities (Tip: you may start with your own mark sheet). è Deliver hard copy to my office, before February xx,

36 References 1. Terry Halpin, Tony Morgan: Information Modeling and Relational Databases, Second Edition. 2 nd Edition. The Morgan Kaufmann Series in Data Management Systems. ISBN: Mustafa Jarrar and Stijn Heymans: Towards Pattern-Based Reasoning For Friendly Ontology Debugging. Journal of Artificial Intelligence Tools. Volume 17. No.4. World Scientific Publishing. Aug Mustafa Jarrar: Mapping ORM Into The SHOIN/OWL Description Logic- Towards A Methodological And Expressive Graphical Notation For Ontology Engineering. In OTM 2007 workshops: Proceedings of the International Workshop on Object-Role Modeling (ORM'07). Pages ( ), LNCS 4805, Springer. ISBN: Portogal. November, Mustafa Jarrar: Towards Automated Reasoning On ORM Schemes. -Mapping ORM Into The DLR_idf Description Logic. In proceedings of the 26th International Conference on Conceptual Modeling (ER 2007). Pages ( ). LNCS 4801, Springer. Auckland, New Zealand. ISBN November Mustafa Jarrar and Stijn Heymans: Unsatisfiability Reasoning In ORM Conceptual Schemes. In Current Trends in Database Technology - EDBT 2006: Proceeding of the IFIP-2.6 International Conference on Semantics of a Networked. Pages ( ). LNCS 4254, Springer. Munich, Germany. ISBN: March Mustafa Jarrar, Maria Keet, and Paolo Dongilli: Multilingual Verbalization Of ORM Conceptual Models And Axiomatized Ontologies. Technical eport. STARLab, Vrije Universiteit Brussel, Feb Mustafa Jarrar: Modularization And Automatic Composition Of Object-Role Modeling (ORM) Schemes. OTM 2005 Workshops: Proceedings of the Object-Role Modeling (ORM'05). Pages ( ). LNCS 3762, Springer. Larnaca, Cyprus. ISBN: November